In many parts of the country, winter-like conditions deposit or form snow and ice on structures, such as roofs of buildings. As a result, snow and ice can pile up on a variety of structures, including roof eaves and intersecting valley areas of roofs. The accumulated volume and weight of ice and snow can cause serious, costly damage to the roofing and other structures.
In addition, as snow and ice melt (typically during the daytime), the resulting flow or dripping of water down or from the roof can form a wide variety of dangerous icicles and ice structures as temperatures later drop (typically in the evening and at night). The resulting icicles and ice structures often fall off the roof or other structures and cause serious damage to property as well as humans and animals.
Often, ice dams forms along roof eaves and intersecting valley areas. Such ice dams can form when: (1) snow accumulates on a roof; (2) heat escapes from the building's interior and melts accumulated snow; and (3) outside ambient temperatures are below freezing, which can cause the melting snow from the heated area to re-freeze along a cold overhang of the roof.
Ice dams can cause a wide variety of serious problems. For example, they can create standing water conditions above the ice dam at a roof overhang. This standing water can cause a variety of types of damage, whether due to weight of the water on the roof or water leakage into the structure or by sliding off of the roof.
These serious and dangerous problems obviously have existed for a very long time. A variety of electrical systems have been developed in the past to try to solve them.
In one prior art electrical system, a heat generating cable is placed along the roof edge, valleys, and other locations. Commonly, the cable is laid in a zig-zag configuration and is exposed and visible on the roof top. With such systems, much of the drip edge area remains unheated and can accumulate dangerous icicles and ice formations. Further, the cable is exposed to the elements, thus leading to ultraviolet degradation of the cable over time. The cable also typically is secured to the roofing by clips that are in turn fastened to the roofing by fasteners penetrating the roof. Commonly, these fasteners are also exposed, creating the risk of leaks. Heater cable can often be stripped off the roof by high winds or sliding snow.
One prior art system by Hot Edge, Inc., is disclosed in U.S. Pat. No. 8,191,319. This system includes a heat cable mounted along the fascia side of the roof to fascia corner. This is accomplished with a two- or three-piece assembly of thin sheet metal (typically low-conducting steel) attached onto the fascia. First, one sheet metal component is attached along the roof's eave and up the roof. A heater cable is mounted within the first sheet metal component, and the second sheet metal component is attached to the fascia plane and clamped to the first sheet metal component to surround the heater cable. This clamping is procedure is awkward and time consuming but is required to establish tight spring pressure contact and thermal conduction between the heater cable and the sheet metal components.
The Hot Edge's system parts are sized and formed depending on the angles of the roof and the fascias, so there are literally hundreds of different configurations from which to choose when ordering a system. The system includes differing structures for twelve differing roof slopes, and the system may be made with or without foam, round or oval holes or no holes at all, long or short fascia flanges, any of 14 colors, two metal thicknesses, and three kinds of metal. The manufacturer recommends purchaser buys and uses a digital protractor to determine the proper system components for a given application.
Many mistakes can happen between the ordering and manufacturing of the Hot Edge system. The installation is tedious and complicated. Errors can easily happen due to poor manufacturing and fit, resulting in poor heat conduction and poor ice melt performance. A broad upward flange of the first component sheet metal component reaches up along the roof with no attachment, which allows an unacceptable waviness (called “oil canning”) in the metal, resulting in an unsightly appearance. The upward extending flange also renders the system vulnerable to damage resulting from wind, and sliding ice and snow.
Another prior art system by Tourangeau (see U.S. Pat. No. 5,391,858) includes a metal eave panel along the building eave with conduits into which heat cable is inserted. The metal components are made of light sheet metal, and the heat cable conduits are mechanically attached to the metal eave panel during installation. The prior art Tourangeau system is very difficult to install. The heat cable must be inserted into the conduit by pushing from one end. An average residential ice dam, however, may be 20′ to 50′ long or more. Inserting cable to penetrate such a structure is typically a difficult and time consuming task.
In addition, the cross-sectional size of the Tourangeau conduit must be loose enough to allow enough room for the cable to slide through the conduit. The excessive space in the conduit required for cable installation inherently leads to a reduction in heat transfer contact between the heater cable and the surrounding conduit, as the self-regulating heater drops down its output to around 50% if it is in “air.” Further to this, sheet metal by itself is considered a relatively poor heat conductor. Securement to the roof is questionable, there is nothing discussed in patent about fastening to the roof; options are subject to ice movement and wind damage.
Yet another prior art system, the Bylin RIM System, consists of a single aluminum heating element mounted to a roof edge and a metal panel cover mounted over the top of the heating element. One lateral side of the heating element abuts and surrounds to some degree the roof edge, and the panel cover typically surrounds heating element, including a portion of the lateral side of the heating element surrounding the roof edge. The panel cover then extends upwardly across and in contact with the upper sides of the heating element and past the heating element upwardly along the roof. The upper portion of the panel cover extending upwardly along the roof is commonly secured to the roof by (i) mounting the upper panel portion on a section of the roof to be further covered by roof structure such as shingles, (ii) securing upper panel portion in place with fasteners penetrating the upper portion and roof support structure below, and (iii) then covering the upper panel portion by mounting shingles over it. A heating cable is mounted in serpentine fashion within three cable passages running along the entire length of the heating element. Thus the three lengths of heating cable heat the aluminum heating element, which in turn heats the panel cover to melt ice and snow in contact with cover.
The applicant has discovered and believes that the heating element of the Bylin RIM System presents a number of problems. They include, for example, that its heating element consists of two relatively thin, planar upper panel support and contact sections spanning between three spaced-apart heating cable channels extending downwardly from the upper panel support sections, and the downwardly extending channels also include, at their lower ends, planar roof contacting sections extending laterally from the lower ends. The relatively thin upper panel support sections, which span across the top of the heating element, can unduly warp, provide insufficient support to, and less than optimal contact with, the upper cover panel cover, and also insufficiently transfer heat through these sections to the upper cover panel. Also, the planar roof contacting sections provide heat loss by consuming heat themselves and also transferring heat to the supporting roof structure in contact with these planar roof contacting sections. In addition, this system provides less than possible heat transfer to its lower edge, which also is in contact with and intended to heat the lower edge of the upper cover panel surrounding that edge to a substantial degree. This also provides no electrolytic isolator to prevent corrosion when a copper cover is used to cover its aluminum heating element.
In another somewhat similar prior art system, by Thermal Technologies, includes a sizeable aluminum heating element that has both a substantial top and a substantial bottom section. The bottom section is secured to the roof by fasteners. The top section has two downwardly extending arms that clip within mating upwardly facing slots along the length of the bottom section. The top and bottom sections cooperatively provide four heating cable passages. Two of the passages are sized to accept one size of heating cable. The other two passages are adapted to accept a differing size of heating cable.
The applicant has discovered and believes that the Thermal Technologies system presents a number of problems too. For example, it is heavy and material intensive, which requires excess material and manufacturing costs. Also, when heater cable is mounted within it, its upper and lower heating element sections are spaced apart by the heater cable, and this leads to substantially reduced, or at least less than optimal, heat transfer from the heater cable to and across the upper heating element section as well as to the portions of the lower heating element section that contact the upper cover panel. In addition, the lower heating element section of this system has a large lower surface in contact with the underlying roof structure, causing heat loss by heating of this structure as well as by heat transfer to that contacting underlying roof structure. Further, this system also provides less than possible and desired heat transfer to its lower edge, which also is in contact with and intended to heat the lower edge of the upper cover panel surrounding that edge to a substantial degree.
Other problems with this system include, for example, its upwardly facing slots, into and through which water can leak and debris can accumulate, which can cause accelerated rotting of the heating cable. Similarly, by providing so much contact between the heating element and underlying roof structure, this system can cause water and humidity to build up in that contact area over time, leading to various problems such as dry rot of adjacent roof materials and corrosion or loosening of the roof attachment fasteners securing the heating element fasteners to the roof.
Another prior art ice prevention system is the Zmesh system from Heatizon (see U.S. Pat. No. 4,581,522). The Heatizon system includes a heatable wire screen installed onto the roof deck and under the roofing materials. In retrofit situations, installation requires removal of the existing roofing, adding to the labor and materials cost. The Heatizon parts are expensive, and the large low-voltage transformers used fail over time; replacement is very expensive. Due to the nature of the installation, the screening is applied under roofing directly onto the roof deck support surface, resulting in a substantial loss of heat down through the cold overhang. Further, when a fastener penetrates both the screening and a metal roof flashing (such as edge trim, valley metal, and plumbing/heating flashings) the system can short out and become inoperable. Further, the Heatizon system utilizes costly additional plies of waterproof roof membranes needed to meet installation requirements. Rooftop installation requires soldering the screening to heavy plate, adding to installation time and opens the possibility of faulty connections. Repair of the Heatizon system requires roofing removal. In addition, due to the folding of the Heatizon screening required at ends of the roof, some roof areas are not heated properly and re-freezing occurs at the eave edge.
Heat from the Heatizon screening must be conducted through the roofing materials. Shingle roofing, however, is not a good conductor, and so the Heatizon system must utilize a large amount of energy to generate the heat needed to reach the melting surface.
Installation requires extending the heatable screen from the eave edge to several feet up the roof surface from the eave edge. It is costly to heat such a broad area, particularly by heating through the roofing material.
Heatizon's prior ice melt system for metal roofs uses a heater wire embedded into a heat sink. This creates an uneven roofing surface at the top edge of the heat sink. It is also expensive to purchase, install, operate, and repair if necessary.
Another prior art system by Heated Roof Panels (see U.S. Pat. No. 7,121,056) uses a principle similar to Heatizon above. This system provides a heatable silicone pad installed onto the roof deck under the roofing. As noted above, this makes installation onto an existing roof very costly due to removal and replacement of the roof. In addition, under-roofing heating elements are an inefficient and costly to operate. This method also suffers not only must generate enough heat to transfer through the upper roofing structure but also incurs heat loss downward through the roof deck into the cold overhang.
The Heated Roof Panel system also uses an expensive underlayment. Typical heater pads are 10″×6′, 8′, and 10.′ Installers are prohibited from penetrating the pad with roofing fasteners, as doing so permanently damages the heater pad and renders it inoperable. Shingles are applied in horizontal rows (courses) with approximately 5″ exposure. Shingle nailing also corresponds with this 5″ course. Therefore, proper shingle nailing (as required by the shingle manufacturer and thus the building code) require penetrating and damaging the heat pad. The manufacturer's proposed solution instructs use an adhesive to attach the shingles over the pads in lieu of nailing. Such a solution can be a violation of the building code. It also makes the roofing shingles more vulnerable to wind blow-off (more common along the roof's perimeter, and where the heat pads are used), and susceptible to damage due to moving ice and snow. Plug-in connections below the roof surface could have problems, and any repair of this device would require expensive removal of the roofing system. Installation requires application from the eave edge to several feet up the roof. Heating this broad area is costly.
The prior art Step De-icing system (see U.S. Pat. No. 5,961,869) is much like the Heatizon and Heated Roof Systems and includes a heating element applied under roofing. It shares the same energy inefficiencies due to inordinate heat loss downward through cold roof overhangs and using a poorly conductive element (such as roofing shingles) to conduct heat to the snow surface. Installation on an existing roof requires removal and replacement of the roofing, and any repairs would also require roofing removal.
This Step De-icing product is made of plastic. It has bus wires that carry the current through the system. When these bus wires are damaged (cut on flashings, penetrated with a roofing fastener, etc.), the system is rendered inoperable. Like the Heatizon system, the Step De-icing system requires expensive transformers that wear out and eventually need replacement. Further, the maximum length possible on one circuit is 33 square feet, which make installation of longer lengths more complicated and time consuming. Similarly, installation requires application from the eave edge to several feet up the roof. This broad area is costly to keep heated, and many circuits and transformers are required for even a small job.
Yet another prior art system is the applicant's Radiant Edge system. The applicant believes that the Radiant Edge system was and is a major advance in the state of the art, but it is a heavy duty system that utilized multiple runs of heating cable through multiple heating cable channels in its heating element. It is also relatively heavier and larger than desired to meet cost, shipping, and structural support objectives in certain applications. Further, it does not allow for easy insertion of, or access to, the heating cable after installation of the heating element cover.